Cardiac mapping is used to locate aberrant electrical pathways and currents within the heart, as well as to diagnose mechanical and other aspects of cardiac activity. Various methods and devices have been described for mapping the heart. Radiofrequency (RF) ablation is used to treat cardiac arrhythmia by ablating and killing cardiac tissue in order to create non-conducting lesions that disrupt the abnormal electrical pathway causing the arrhythmia.
U.S. Pat. Nos. 5,546,951 and 6,066,094 to Ben-Haim, and European Patent 0 776 176 to Ben-Haim et al., which are assigned to the assignee of the present patent application and are incorporated herein by reference, describe methods for sensing an electrical property of heart tissue, for example, local activation time, as a function of the precise location within the heart. The data are acquired with a catheter that has electrical and location sensors in its distal tip, and which is advanced into the heart. Techniques for sensing cardiac electrical activity are also described in U.S. Pat. No. 5,471,982 to Edwards et al., commonly-assigned U.S. Pat. Nos. 5,391,199 and 6,066,094 to Ben-Haim, U.S. Pat. No. 6,052,618 to Dahlke et al., and in PCT Patent Publications WO94/06349 and WO97/24981, which are incorporated herein by reference.
Methods for creating a map of the electrical activity of the heart based on these data are described in U.S. Pat. Nos. 6,226,542 and 6,301,496 to Reisfeld, which are assigned to the assignee of the present patent application and are incorporated herein by reference. As indicated in these patents, location and electrical activity is preferably initially measured on about 10 to about 20 points on the interior surface of the heart. These data points are then generally sufficient to generate a preliminary reconstruction or map of the cardiac surface to a satisfactory quality. The preliminary map is often combined with data taken at additional points in order to generate a more comprehensive map of the heart's electrical activity. In clinical settings, it is not uncommon to accumulate data at 100 or more sites to generate a detailed, comprehensive map of heart chamber electrical activity. The generated detailed map may then serve as the basis for deciding on a therapeutic course of action, for example, tissue ablation, which alters the propagation of the heart's electrical activity and restores normal heart rhythm. Methods for constructing a cardiac map of the heart are also disclosed in U.S. Pat. Nos. 5,391,199 and 6,285,898 to Ben-Haim, and in U.S. Pat. Nos. 6,368,285 and 6,385,476 to Osadchy et al., which are assigned to the assignee of the present patent application and are incorporated herein by reference.
Catheters containing position sensors may be used to determine the trajectory of points on the cardiac surface. These trajectories may be used to infer motion characteristics such as the contractility of the tissue. As disclosed in U.S. Pat. No. 5,738,096 to Ben-Haim, which is assigned to the assignee of the present application and which is incorporated herein by reference, maps depicting such motion characteristics may be constructed when the trajectory information is sampled at a sufficient number of points in the heart.
European Patent Application EP 1 125 549 and corresponding U.S. patent application Ser. No. 09/506,766 to Ben-Haim et al., which are assigned to the assignee of the present patent application and are incorporated herein by reference, describe techniques for rapidly generating an electrical map of a chamber of the heart. The catheter used for these techniques is described as comprising a contact electrode at the distal tip of the catheter and an array of non-contact electrodes on the shaft of the catheter near the distal end. The catheter also comprises at least one position sensor. Information from the non-contact electrodes and contact electrode is used for generating a geometric and electrical map of the cardiac chamber.
U.S. Pat. No. 5,848,972 to Triedman et al., which is incorporated herein by reference, describes a method for endocardial activation mapping using a multi-electrode catheter. A multi-electrode catheter is advanced into a chamber of the heart. Anteroposterior and lateral fluorograms are obtained to establish the position and orientation of each of the electrodes. Electrograms are recorded from each of the electrodes in contact with the cardiac surface relative to a temporal reference such as the onset of the P-wave in sinus rhythm from a body surface ECG. After the initial electrograms are recorded, the catheter is repositioned, and fluorograms and electrograms are once again recorded. An electrical map is then constructed from the above information.
U.S. Pat. No. 4,649,924 to Taccardi, which is incorporated herein by reference, describes a method for the detection of intracardiac electrical potential fields. The '924 patent is illustrative of non-contact methods that have been proposed to simultaneously acquire a large amount of cardiac electrical information. In the method of the '924 patent, a catheter having a distal end portion is provided with a series of sensor electrodes distributed over its surface and connected to insulated electrical conductors for connection to signal sensing and processing means. The size and shape of the end portion are such that the electrodes are spaced substantially away from the wall of the cardiac chamber. The method of the '924 patent is said to detect the intracardiac potential fields in only a single cardiac beat.
PCT application WO 99/06112 to Rudy, which is incorporated herein by reference, describes an electrophysiological cardiac mapping system and method based on a non-contact, non-expanded multi-electrode catheter. Electrograms are obtained with catheters having from 42 to 122 electrodes.
U.S. Pat. No. 5,297,549 to Beatty et al., which is incorporated herein by reference, describes a method and apparatus for mapping the electrical potential distribution of a heart chamber. An intra-cardiac multielectrode mapping catheter assembly is inserted into the heart. The mapping catheter assembly includes a multi-electrode array with an integral reference electrode, or, preferably, a companion reference catheter. In use, the electrodes are deployed in the form of a substantially spherical array. The electrode array is spatially referenced to a point on the endocardial surface by the reference electrode or by the reference catheter, which is brought into contact with the endocardial surface. Knowledge of the location of each of the electrode sites on the array, as well as a knowledge of the cardiac geometry is determined by impedance plethysmography.
U.S. Pat. Nos. 5,385,146 and 5,450,846 to Goldreyer, which are incorporated herein by reference, describe a catheter that is said to be useful for mapping electrophysiological activity within the heart. The catheter body has a distal tip which is adapted for delivery of a stimulating pulse for pacing the heart or for ablating tissue in contact with the tip. The catheter further comprises at least one pair of orthogonal electrodes to generate a difference signal indicative of the local cardiac electrical activity adjacent the orthogonal electrodes.
U.S. Pat. No. 5,662,108 to Budd et al., which is incorporated herein by reference, describes a process for measuring electrophysiological data in a heart chamber. The method involves, in part, positioning a set of active and passive electrodes in the heart; supplying current to the active electrodes, thereby generating an electric field in the heart chamber; and measuring this electric field at the passive electrode sites. In one of the described embodiments, the passive electrodes are contained in an array positioned on an inflatable balloon of a balloon catheter.
U.S. Pat. No. 6,226,543 to Gilboa et al., which is incorporated herein by reference, describes a method of recording and displaying in the context of an image a location of a point-of-interest in a body during an intra-body medical procedure. The method employs a catheter inserted into a portion of the body, and an imaging instrument for imaging the portion of the body. The point-of-interest is displayed in the context of the image generated by the imaging instrument.
U.S. Pat. No. 5,718,241 to Ben-Haim, U.S. Pat. No. 6,216,027 to Willis et al., U.S. Pat. No. 6,004,269 to Crowley at al., and U.S. Pat. No. 5,769,846 to Edwards et al., which are incorporated herein by reference, describe techniques for directing a catheter to a desired treatment site in the heart and ablating tissue at the site. U.S. Pat. No. 6,353,751 to Swanson et al., which is incorporated herein by reference, describes systems for guiding a movable electrode within an array of electrodes located within the body.